German Patent Publication DE-C2 36 30 887 describes a position measuring system in the form of an interferometer using integrated optics construction. A substrate arrangement is described having a waveguide for the measuring beam, a laser connected at one end of the waveguide and a decoupling or coupling grating located at the other end of the waveguide. A so-called reference waveguide is obtained from the measuring waveguide by use of a coupler. A mirrored edge of the substrate terminates the reference waveguide and this forms a mirror for the reference waveguide. A disadvantage associated with such a system is that it is not easy to produce mirrors or Bragg reflectors in an integrated optical device. Also, systems requiring lenses also have problems in manufacture and adjustment.